To reduce nuclear-proliferation concerns, it is desirable to curtail the worldwide use of high-enriched uranium (HEU) by substituting low-enriched uranium (LEU) for research reactor fuel and medical isotope targets. Low-enriched uranium contains <20% 235U. Presently, most research reactors have converted their driver fuel from HEU to LEU; however, several high power reactors require fuel with uranium densities not attainable with dispersion designs. Fuel designs consisting of a solid uranium alloy core rather than uranium alloy—Al dispersions as the fissile part of the fuel will enable conversion of most remaining HEU fueled reactors.
Currently, most of the world's supply of 99Mo for medical diagnostics use is produced by fissioning the 235U in HEU targets, generally enriched to 93% 235U. After irradiation, the 99Mo is separated from the uranium and activation and fission products. Targets have been developed that use uranium alloys to allow the facile transition from HEU to LEU. These targets have been so successful that many producers have completed feasibility studies and moved into planning for their conversion to LEU.